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Những nguyên nhân đọc sai giá trị pH

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Những nguyên nhân đọc sai giá trị pH0 out of 50 based on 0 voters.


Chemical Inc., a chemical manufacturer, is losing raw materials to what they thought were erroneous pH readings. They have a pH control system in place that activates a solenoid valve in the bottom of the tank once a specific pH is reached. Shortly after the tank started emptying, they saw the pH spike and manually shut off the valve and scrapped the batch. After this occurred a couple of times, they began rechecking the pH of the raw material and found it was exactly where it was supposed to be. They even double checked it with a separate tester. So, they asked for a warranty replacement on the pH probe. Upon troubleshooting, it was determined the solenoid valve was starting to go bad. As the valve wore out, stray electrical signals entered the mixing tank and the pH probe interpreted the stray signal as a change in pH.

What should the team use to avoid erroneous readings from stray voltages in the future?

    A. An air-actuated ball valve (such as 01347-74) to avoid stray electrical signals

    B. A solution-grounded pH probe (such as 27018-00) to combat electrical interference

    C. A high-accuracy fast-response pH probe (such as 27040-02) to read quickly before any electrical noise can interfere

    D. A new solenoid valve overall (such as 98604-50) since the issue was the old solenoid valve

Answers:

    A. An air-actuated ball valve (such as 01347-74) to avoid stray electrical signals 
    Incorrect. This would require that the pH controller is set up to activate an air compressor. More engineering would need to go into putting an air supply line in place along with the compressor.

    B. A solution-grounded pH probe (such as 27018-00) to combat electrical interference
    Correct!
     Addition of a ground wire would allow any stray electrical signals in the solution to go to the grounding wire rather than the pH probe itself, eliminating any unstable or inaccurate readings.

    C. A high-accuracy fast-response pH probe (such as 27040-02) to read quickly before any electrical noise can interfere
    Incorrect. The fast response time of this probe would make electrical noise and provide jumpier readings.

    D. A new solenoid valve overall (such as 98604-50) since the issue was the old solenoid valve
    Incorrect. Although Chemical Inc. may want to replace the solenoid also, there is a better solution. Additionally, we are unsure of chemical compatibility and this is only a PVC and EPDM valve.